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Comment by galkk | Hacker News Reader

Let me give you an example.

I need to write a cron expression like once in couple years. So, I don't have working memory of it. So, to write it, I need to

1. Google "cron run something periodically".

2. Filter spam such as geeksforgeeks and irrelevant stackoverflows

3. Find either good enough approximation

4. If didn't work, go to cron man and start reading it. Example that I look for is 3rd from below in examples table https://docs.oracle.com/cd/E12058_01/doc/doc.1014/e12030/cro...

I can go to chatgpt/copilot and directly ask what I need

"Tell me a cron expression to run command on each third Monday of a month and explain it"

and it will give me good enough approximation right from the start. I won't need to fight popups that will shame me for using adblockers, I won't need to go through tons of spam. I will get much better headstart, that will save my time and energy.

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> "Tell me a cron expression to run command on each third Monday of a month and explain it"

ChatGPT responds:

> 0 0 0 ? * MON#3 *

Regarding MON#3, it explains: "Day of the week (MON#3): This is the crucial part of the expression. We use MON to specify that we want the command to run on a Monday. Then we append #3 to indicate that we want the third occurrence of Monday. This ensures that the command will run on the third Monday of the month."

It does not mention though, even with the smallest hint, that standard cron does not support this syntax. Or a 7-field syntax.

(By "standard cron" I mean Vixie cron derivatives like the one that ships with Debian)

The correct answer in this case would have been: "This is not possible with standard cron syntax alone. You can either use a different cron implementation that supports MON#3, or schedule for every Monday, but then in your script check if it's the third Monday."

But can you trust that the expression it generated is accurate and it's not lying to you?

I'd rather use something like https://crontab.guru/ to verify my syntax, thus I have it bookmarked for the 1-2 times a year it comes up.

As I said - it gives me very good initial approximation, so I can go to docs with an example that I'm trying to figure.

> Tell me a cron expression to run command on each third Monday of a month

An LLM is probably the only thing which could tell you this.

I gotta say, LLMs are an epic solution to things like cron expressions, regexes, and date-time formatting templates.

Yes, I'm sure in 2-3 years I'll be finding plenty of regexes analogous to that cron expression, like one matching balanced parentheses.

Why would only an LLM be able to tell you this?

Because it needs to be hallucinated.

I don't understand, a Stack Overflow post could tell you the same thing as the LLM. Or are you just being sarcastic? Recent LLMs are fine in terms of smaller things like cron or regex, I use them daily, but yes, for larger pieces of code, they're more likely to be incorrect.

I mean yes an SO answer could also be wrong, or you could ask a human pathological liar, but these are much less likely to begin with, and it's far less likely they could "explain" their answer convincingly.

> Recent LLMs are fine in terms of smaller things like cron

This is obviously false given the contents of this thread.

Indeed, SO (well, SU) got this right: https://superuser.com/questions/428807/run-a-cron-job-on-the...

And crontab(5) explicitly calls out why this is impossible:

       Note: The day of a command's execution can be specified by two fields —
       day  of  month,  and  day  of week.  If both fields are restricted (ie,
       aren't *), the command will be run when either field matches

> This is obviously false given the contents of this thread.

Not in my experience. GPT4 works a lot better than previous LLMs. Have you used GPT4 yet? Typically in my experience people who talk about LLMs not being that useful (or "pathological liars") have not used them recently, or at all. So, I mean, not a useful opinion worth considering then.

Sorry, I'm talking about the actual claims in this thread, not your religion.

I have an "actual claim" in this thread, but because mine doesn't agree with your beliefs about LLMs being bad, you ironically claim it's my religion instead, lol.

Your claim then seems to be that galkk is just plain lying? That seems uncharitable.

Lying? No, I never said that, their version of ChatGPT (3.5 which is older) or Copilot (the Codex model it uses is much older) might very well be hallucinating wrong answers, sure. But my claim was that the newer models such as GPT 4 work well for certain classes of problems, so no, it's not "obviously false" that they don't work, which is what you claimed. Does GPT 4 get stuff wrong too sometimes? Sure, I never claimed they're perfect either, but unlike people in this thread, it has worked well generally for me based on my experience, but if you want to discount my experience and only listen to other people who confirm your beliefs, you do you.

This is absolutely what I imagine using Copilot for and also exactly why I don't understand the rapturous praise for increasing productivity. I have no doubt it will speed up the tasks I only need to do once or twice a year. I look forward to it! But until then where are these productivity gains people are talking about?

I'm working on a product and a lot of the code was written by ChatGPT, to be honest. It sped up my work by 3x, and I could ask it very specific questions about the code as well, including giving me multiple ways to optimize it. If you're working with specific libraries and languages, it can work great.

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